For tuning to and receiving signals from a satellite broadcasting station, it is necessary to adjust the direction of a parabolic antenna and for this purpose there have been proposed mounting devices which provide for driving the antenna to the proper position.
A conventional device has a linear actuator mounted between an antenna pole and the backside of the antenna, but this device is limited in the gyratory angle (approximately to 100.degree.), thereby fails to cover all of the broadcasting satellites. In addition, the conversion of the linear motion of this device to rotary motion causes a large variation in the direction of movement in the travel of the actuator from between its opposite terminal ends, and thereby reduces the efficiency of the device.
On the other hand, various devices have been proposed which employ a rotary actuator, but such devices have problems in either maintenance or installation, or both. Where the rotary drive is exposed to the atmospheric conditions without suitable measures for sealing the rotary mechanism against rusting by rain or snow and intrusion of rainwater, there is also difficulty in providing adequate lubrication of the rotating parts. Furthermore, the prior devices of this type have presented problems in mounting the antenna directly to the gyratory shaft, for example, giving rise to problems such as a large overhang, power loss and deterioration in the rigidity of the mount.
A dual system type antenna support device has been proposed in Japanese laid-out patent application No. 187104/1985, which provides for independent adjustment of the face of the antenna in addition to gyratory movements. Since the axis of gyration is vertical, the adjustment of the angle of elevation of the face is necessitated after each gyratory movement. Consequently, the mechanism is difficult to adjust to properly focus on the satellite without complicated and expensive internal construction.